As automation increases in industry and increased complexity when choosing materials lasers become increasingly important. Especially promising is the Nd:YAG laser, which is very well suited to be integrated with a robot, but also carbon dioxide and excimer lasers are important for industry. There are also other lasers, which industrial applicability is high.
In this kind of inventions, there is often a lens having the purpose of focussing the laser beam in desired way. A consequence of the presence of the lens is that the laser beam appears with a waist, i.e. a shape which in the direction of the beam first presents a narrowing feature, which thereafter becomes wider. The processing effect of the laser beam is naturally at maximum where the beam presents its smallest surface. Therefore, it is interesting to be able to position the laser simply and effectively in order to accomplish this.
Today, one way of measuring the position of the focus point position, which should be the same as the tool center point of the robot, is based on the assistance of a visual assisting laser and manually moving the robot in order to position the focus point position in a well-defined position in space. This is normally time-consuming and gives an obvious lack of precision.
In SE-447 972 a method for detecting a focus point position for a device processing with a laser is presented. It is characterized by a light shielding element, which can shield a fraction of the laser beams and a light sensor, produces an output signal. The output signal is proportional to the amount of laser light having passed through the light shielding element. The searching for focus is arranged so that at least the light shielding element or the light sensor is moved in direction of the optical axis for detection of the position, at which the output signal of the light sensor is at its maximum or at its minimum. Based on the minimum or maximum output signal of the light sensor the focus point position is detected. It should be noted that the invention described in this document only detects the focus point position and does not deal with the shape or power distribution of the laser beam.